Hybrid pumped hydro storage systems modeling, optimization and cost-benefit analysis

Today, the increasing energy demand and the necessity to combat climate change are driving greater interest in sustainable energy solutions. Policies to reduce dependence on fossil fuels are increasing the use of renewable energy sources. In this direction, energy storage systems play a critical role in ensuring energy security, maintaining supply-demand balance, and integrating renewable energy sources. Particularly, Pumped Hydroelectric Storage (PHS) systems stand out as a long-lasting, environmentally friendly, and high-capacity storage method. Considering Turkey's hydroelectric potential, the conversion of existing reservoirs into PHS systems offers a significant opportunity for energy continuity. This study comprehensively examines the conversion of hydroelectric reservoirs in Turkey into PHS systems from technical, economic, and environmental perspectives. Firstly, site selection for the second reservoir was carried out. Then, the energy potential of the PHS system was determined through detailed mathematical modeling that considers hydraulic losses. The integration with hybrid energy systems was evaluated, and cost and efficiency analyses were conducted under different scenarios. This research makes a significant contribution to the literature by addressing site selection, technical modeling, and economic analysis together. Batman Dam and Hydroelectric Power Plant were selected as the pilot region. A Geographic Information System (GIS)-based multi-criteria decision-making analysis was applied to determine the suitable second reservoir area. Geological and land use maps were created using the Digital Elevation Model (DEM), and the potential reservoir area was determined. To calculate the energy potential, a detailed mathematical model including hydraulic losses, evaporation, and precipitation effects was developed in the Simulink environment. According to the mathematical modeling results, the installed capacity of the designed PHS system was calculated as 1299 kW, and the system was found to provide 6500 kWh of energy for 5 hours. The obtained energy potential data were integrated into the Hybrid Optimization of Multiple Energy Resources software, and technical and economic feasibility analyses were conducted under three different scenarios: solar-wind-generator-PHS, solar-generator-PHS, and wind-generator-PHS systems. Each system was comparatively analyzed in terms of payback period, Levelized Cost of Energy (COE), and Net Present Cost (NPC). The results showed that PHS integration reduced energy costs by up to 30%. The return on investment (ROI) of the solar-wind-generator-PHS system reached 48.2%, while the payback period was approximately 2 years. Additionally, the analyses determined that carbon emissions were reduced by up to 66.2%. These findings indicate that PHS integration into hybrid energy systems provides significant economic and environmental benefits, contributing to sustainable energy policies. In future studies, comparing PHS systems with different energy storage methods and validating models with field data will contribute to a more comprehensive evaluation of the system's feasibility. Furthermore, the integration of alternative renewable energy solutions such as floating PV systems can be examined to investigate potential advantages in terms of efficiency and water loss management.